Label-free detection of endocrine disrupting chemicals by integrating a competitive binding assay with a piezoelectric ceramic resonator

Active colorimetric lipid-coated polyaniline nanoparticles for redox state sensing in cancer cells

Herein, lipid-coated polyaniline (LiPAni) nanoparticles were fabricated to monitor the redox state of cancer cells. To confirm the characteristics of LiPAni, we firstly analyzed the size and chemical structures of the LiPAni nanoparticles. The absorbance properties of the LiPAni nanoparticles were observed to vary with the pH conditions. Furthermore, cell viability tests conducted with breast cancer cell lines showed that the cell viability of the cells with LiPAni nanoparticles was dramatically increased compared to those with the Tween80-coated polyaniline nanoparticles (TPAni) as a control. Subsequently, the colors of the LiPAni nanoparticles were observed and analyzed using spectroscopic methods. Finally, in order to investigate the more accurate sensing of the redox state using the color changes of the LiPAni nanoparticles with cancer cell lines, dark field microscopic images and scattering spectra were recorded at the single nanoparticle scale. For the TPAni nanoparticles, there was only a change in brightness and no change in color, but for the LiPAni nanoparticles, there was a change of color from yellow to pink in the dark field images.

Electrochemical biosensor for detection of 17β-estradiol using semi-conducting polymer and horseradish peroxidase

A convenient electrochemical sensing pathway for 17β-estradiol detection was investigated. The system is based on a conducting polymer and horseradish peroxidase (HRP) modified platinum (Pt) electrode. The miniature estradiol biosensor was developed and constructed through the immobilization of HRP in an electroactive surface of the electrode covered with electroconducting polymer – poly(4,7-bis(5-(3,4-ethylenedioxythiophene)thiophen-2-yl)benzothiadiazole). The detection strategy is based on the fact that 17β-estradiol (E2) and pyrocatechol (H₂Q) are co-substrates for the HRP enzyme. HRP, which does not react with E2, in the presence of H₂O₂ catalyses the oxidation of H₂Q to o-benzoquinone (Q). With the optimized conditions, such constructed biosensing system demonstrated a convenient level of sensitivity, selectivity in a broad linear range – 0.1 to 200 μM with a detection limit of 105 nM. Furthermore, the method was successfully applied for hormone detection in the presence of potential interfering compounds (ascorbic acid, estriol, estrone, uric acid and cholesterol).

A convenient electrochemical sensing pathway for 17β-estradiol detection was investigated.

Advances in sensing and biosensing of bisphenols: A review

Bisphenols (BPs) are well known endocrine disrupting chemicals (EDCs) that cause adverse effects on the environment, biotic life and human health. BPs have been studied extensively because of an increasing concern for the safety of the environment and for human health. They are major raw materials for manufacturing polycarbonates, thermal papers and epoxy resins and are considered hazardous environmental contaminants. A vast array of sensors and biosensors have been developed for the sensitive screening of BPs based on carbon nanomaterials (carbon nanotubes, fullerenes, graphene and graphene oxide), quantum dots, metal and metal oxide nanocomposites, polymer nanocomposites, metal organic frameworks, ionic liquids and molecularly imprinted polymers. This review is devoted mainly to a variety of sensitive, selective and reliable sensing and biosensing methods for the detection of BPs using electrochemistry, fluorescence, colorimetry, surface plasmon resonance, luminescence, ELISAs, circular dichroism, resonance Rayleigh scattering and adsorption techniques in plastic products, food samples, food packaging, industrial wastes, pharmaceutical products, human body fluids and many other matrices. It summarizes the advances in sensing and biosensing methods for the detection of BPs since 2010. Furthermore, the article discusses challenges and future perspectives in the development of novel sensing methods for the detection of BP analogs.

Development of Novel Piezoelectric Biosensor Using PZT Ceramic Resonator for Detection of Cancer Markers

A novel biosensor based on piezoelectric ceramic resonator was developed for direct detection of cancer markers in the study. For the first time, a commercially available PZT ceramic resonator with high resonance frequency was utilized as transducer for a piezoelectric biosensor. A dual ceramic resonators scheme was designed wherein two ceramic resonators were connected in parallel: one resonator was used as the sensing unit and the other as the control unit. This arrangement minimizes environmental influences including temperature fluctuation, while achieving the required frequency stability for biosensing applications. The detection of the cancer markers Prostate Specific Antigen (PSA) and α-Fetoprotein (AFP) was carried out through frequency change measurement. The device showed high sensitivity (0.25 ng/ml) and fast detection (within 30 min) with small samples (1 μl), which is compatible with the requirements of clinical measurements. The results also showed that the ceramic resonator-based piezoelectric biosensor platform could be utilized with different chemical interfaces, and had the potential to be further developed into biosensor arrays with different specificities for simultaneous detection of multiple analytes.

Au Nanoparticles Decorated TiO2 Nanotube Arrays as a Recyclable Sensor for Photoenhanced Electrochemical Detection of Bisphenol A

A photorefreshable and photoenhanced electrochemical sensing platform for bisphenol A (BPA) detection based on Au nanoparticles (NPs) decorated carbon doped TiO2 nanotube arrays (TiO2/Au NTAs) is described. The TiO2/Au NTAs were prepared by quick annealing of anodized nanotubes in argon, followed by controllable electrodeposition of Au NPs. The decoration of Au NPs not only improved photoelectrochemical behavior but also enhanced electrocatalytic activities of the resulted hybrid NTAs. Meanwhile, the high photocatalytic activity of the NTAs allowed the electrode to be readily renewed without damaging the microstructures and surface states after a short UV treatment. The electrochemical detection of BPA on TiO2/Au NTAs electrode was significantly improved under UV irradiation as the electrode could provide fresh reaction surface continuously and the further increased photocurrent resulting from the improved separation efficiency of the photogenerated electron-hole pairs derived from the consumption of holes by BPA. The results showed that the refreshable TiO2/Au NTAs electrode is a promising sensor for long-term BPA monitoring with the detection limit (S/N = 3) of 6.2 nM and the sensitivity of 2.8 μA·μM(-1)·cm(-2).

Aptamer-functionalized nanoporous gold film for high-performance direct electrochemical detection of bisphenol A in human serum

In the present work, a highly sensitive and selective biosensor based on aptamer-functionalized nanoporous gold film (NPGF) was successfully developed for direct electrochemical detection of bisphenol A (BPA). NPGF was prepared by dealloying Ag from Au/Ag alloy leaf in concentrated nitric acid. The obtained NPGF was attached onto glassy carbon electrode and then was functionalized with BPA-specific aptamer via the formation of Au-S bond. The fabrication of the sensor was characterized by scanning electron microscopy and X-ray photoelectron spectroscopy. NPGF exhibited excellent electrocatalytic activity towards the redox reaction of BPA, which ensured high sensitivity of the sensor. The aptamer-captured BPA showed a pair of redox peaks around 0.35/0.28 V (vs. Ag/AgCl). The experimental parameters in terms of aptamer concentration, reaction time, pH, and temperature were optimized. The calibration plot showed a linear range from 0.1 nM to 100 nM BPA with a remarkable detection limit of 0.056±0.004 nM BPA. Particularly, the successful application of the developed sensor for the detection of BPA in human serum samples suggests its promising potential for clinical diagnosis.

A new label-free strategy for a highly efficient chemiluminescence immunoassay

A new label-free chemiluminescence (CL) immunoassay method which is based on the co-immobilization of a capture antibody and horseradish peroxidase (HRP) on the Au nanoparticle–chitosan composite interface is proposed for the cheap, fast and convenient detection of proteins.